Move services to /var/service
Summary:
In Debian Bullseye, the Debian package creates /etc/service as a symlink to
/etc/runit/runsvdir/current. The /etc/runit folder is a byzantine complex
construction with for example a "current" and "default" set of services.
This change switches to an independent /var/service folder, where images
can maintain a simpler structure.
This fixes issue to build the image using BuildKit, as this mechanism
doesn't allow to replace a symlink by a directory.
Ref T1679.
Test Plan: Build image with environment variable DOCKER_BUILDKIT set to 1.
Reviewers: dereckson
Reviewed By: dereckson
Maniphest Tasks: T1679
Differential Revision: https://devcentral.nasqueron.org/D2525